<?php

/**
 * $xml = new xml();
 * $res = $xml->xml_unserialize($data);
 */
class xml {

    var $parser;
    var $document;
    var $parent;
    var $stack;
    var $last_opened_tag;

    public function xml() {
        $this->parser = xml_parser_create();
        xml_parser_set_option($this->parser, XML_OPTION_CASE_FOLDING, false);
        xml_set_object($this->parser, $this);
        xml_set_element_handler($this->parser, 'open', 'close');
        xml_set_character_data_handler($this->parser, 'data');
    }

    public function destruct() {
        xml_parser_free($this->parser);
    }

    /**
     * unserialize
     * @param xml字符串
     * @return array
     */
    public function xml_unserialize($xml) {
        $data = $this->parse($xml);
        $this->destruct();
        return $data;
    }

    /**
     * serialize
     * @param $data 数组
     * @return string
     */
    public function xml_serialize(&$data, $level = 0, $prior_key = NULL) {
        if ($level == 0) {
            ob_start();
            echo "<?xml version=\"1.0\" encoding=\"" . CHARSET . "\"?>\n<root>", "\n";
        }
        while (list($key, $value) = each($data)) {
            if (!strpos($key, ' attr')) {
                if (is_array($value) and array_key_exists(0, $value)) {
                    $this->xml_serialize($value, $level, $key);
                } else {
                    $tag = $prior_key ? $prior_key : (is_numeric($key) ? 'item' : $key);
                    echo str_repeat("\t", $level), '<', $tag;
                    if (array_key_exists("$key attr", $data)) {
                        while (list($attr_name, $attr_value) = each($data["$key attr"])) {
                            echo ' ', $attr_name, '="', htmlspecialchars($attr_value), '"';
                        }
                        reset($data["$key attr"]);
                    }
                    if (is_null($value)) {
                        echo " />\n";
                    } elseif (!is_array($value)) {
                        echo '>', htmlspecialchars($value), "</$tag>\n";
                    } else {
                        echo ">\n", $this->xml_serialize($value, $level + 1), str_repeat("\t", $level), "</$tag>\n";
                    }
                }
            }
        }
        reset($data);
        if ($level == 0) {
            $str = &ob_get_contents();
            ob_end_clean();
            return $str . '</root>';
        }
    }

    public function parse(&$data) {
        $this->document = array();
        $this->stack = array();
        $this->parent = &$this->document;
        return xml_parse($this->parser, $data, true) ? $this->document : NULL;
    }

    public function open(&$parser, $tag, $attributes) {
        $this->data = '';
        $this->last_opened_tag = $tag;
        if (is_array($this->parent) && array_key_exists($tag, $this->parent)) {
            if (is_array($this->parent[$tag]) && array_key_exists(0, $this->parent[$tag])) {
                $key = $this->count_numeric_items($this->parent[$tag]);
            } else {
                if (array_key_exists("$tag attr", $this->parent)) {
                    $arr = array('0 attr' => &$this->parent["$tag attr"], &$this->parent[$tag]);
                    unset($this->parent["$tag attr"]);
                } else {
                    $arr = array(&$this->parent[$tag]);
                }
                $this->parent[$tag] = &$arr;
                $key = 1;
            }
            $this->parent = &$this->parent[$tag];
        } else {
            $key = $tag;
        }

        if ($attributes) {
            $this->parent["$key attr"] = $attributes;
        }
        $this->parent = &$this->parent[$key];
        $this->stack[] = &$this->parent;
    }

    public function data(&$parser, $data) {
        if ($this->last_opened_tag != NULL) {
            $this->data .= $data;
        }
    }

    public function close(&$parser, $tag) {
        if ($this->last_opened_tag == $tag) {
            $this->parent = $this->data;
            $this->last_opened_tag = NULL;
        }
        array_pop($this->stack);
        if ($this->stack) {
            $this->parent = &$this->stack[count($this->stack) - 1];
        }
    }

    public function count_numeric_items(&$array) {
        return is_array($array) ? count(array_filter(array_keys($array), 'is_numeric')) : 0;
    }

}

?>